Expand upon existing `ImageSubscript` support (Metal, GLSL, SPIRV) (#4408)

* Add additional `ImageSubscript` features:

1. Added ImageSubscript support for Metal & a test case
    * Merge GLSL/SPIRV/Metal `ImageSubscript` legalization pass
2. Added multisample support to glsl/spirv/metal for when using ImageSubscript
    * Added in this PR since the overhaul of the code merges together GLSL/SPIRV/Metal implementation
3. Fixed minor metal texture `Load`/`Read` bugs
    * [HLSL methods of access do not support subscript accessor for texture cube array](https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/texturecubearray)
    * removed swizzling of uint/int/float
    * other odd bugs which were causing compile errors

note: Compute tests do not work due to what seems to be the GFX backend (causes crash without error report). The tests are disabled.

* disable LOD with texture 1d

seems that LOD for 1d textures need to be a compile time constant as per an error metal throws

* syntax error in hlsl.meta

* static_assert alone with intrinsic_asm error

provides cleaner errors
Note: `static_assert` seems to be unstable and not be fully respected (still require `intrinsic_asm` to avoid a stdlib compile error)

* change comment to `// lod is not supported for 1D texture

* add `static_assert` in related code gen paths

* address review

* address review

* add asserts as per review comment, NOTE: unclear if these should be release 'asserts' as well

1 files changed, 6 insertions, 5 deletions

diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index c0541f4c4..a4ea100dc 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -4841,17 +4841,18 @@ namespace Slang
         return inst;
     }
 
-    IRInst* IRBuilder::emitImageLoad(IRType* type, IRInst* image, IRInst* coord)
+    /// @param params An ordered list of imageLoad parameters { image, coord, [optional] seperateArrayCoord, [optional] seperateSampleCoord }
+    IRInst* IRBuilder::emitImageLoad(IRType* type, ShortList<IRInst*> params)
     {
-        auto inst = createInst<IRImageLoad>(this, kIROp_ImageLoad, type, image, coord);
+        auto inst = createInst<IRImageLoad>(this, kIROp_ImageLoad, type, params.getCount(), params.getArrayView().getBuffer());
         addInst(inst);
         return inst;
     }
 
-    IRInst* IRBuilder::emitImageStore(IRType* type, IRInst* image, IRInst* coord, IRInst* value)
+    /// @param params An ordered list of imageStore parameters { image, coord, value, [optional] seperateArrayCoord, [optional] seperateSampleCoord }
+    IRInst* IRBuilder::emitImageStore(IRType* type, ShortList<IRInst*> params)
     {
-        IRInst* args[] = {image, coord, value};
-        auto inst = createInst<IRImageStore>(this, kIROp_ImageStore, type, 3, args);
+        auto inst = createInst<IRImageStore>(this, kIROp_ImageStore, type, params.getCount(), params.getArrayView().getBuffer());
         addInst(inst);
         return inst;
     }